The present invention relates to multi-dielectric films for semiconductor devices and methods of fabricating the multi-dielectric film, and more particularly, to multi-dielectric films with a high dielectric constant (k).
As semiconductor devices become more highly integrated and have a higher capacity, thin films with a high dielectric constant (k) have been used as, for example, gate insulating films of transistors, dielectric films of capacitors and/or gate dielectric films of non-volatile memory devices. When such high-k thin films are used, leakage current generated in the thin films can generally be limited where a thin equivalent oxide thickness is maintained.
Metal oxide may be used for a high-k thin film. For example, an aluminum oxide film (Al2O3), a hafnium oxide film (HfO2) and a zirconium oxide film (ZrO2) have been evaluated for such applications.
As the hafnium oxide film is generally easily crystallized at high temperature, leakage current may be increased. In addition, the hafnium oxide film generally cannot be used for a thin film that requires a high dielectric constant of more than approximately 20. The zirconium oxide film has a high dielectric constant of approximately 35. However, as its crystalline structure is not elaborate, zirconium oxide generally has poor surface morphology, which, in turn, may increase leakage current.
In order to enhance the reliability of the zirconium oxide film, a multi-dielectric film, which includes the zirconium oxide film and an aluminum oxide film, has been proposed. However, when the aluminum oxide film is formed on the zirconium oxide film, because of the crystalline structure of the zirconium oxide, the zirconium oxide film may not be sufficiently crystallized. Even if the zirconium oxide film is crystallized, oxygen required to form the aluminum oxide film may pass through the zirconium oxide film due to large-sized crystal particles. As a result, oxygen that passed through the zirconium oxide film may oxidize an underlying structure of the zirconium oxide film. As a result, leakage current may be increased.